It is desirable to provide a keypad with many outputs (e.g., numerals, letters, punctuation marks, and predefined operations) in a small space, without excessive mechanical complexity, material or service costs. Ideally, each input should be accompanied by a single and well-defined tactile feedback, and each key should be easily and reliably manipulated by a single human finger to provide a desired input. One of the most difficult aspects of keypad design is providing the “right” tactile feel; This apparently simple task is notorious within the industry and widely known without, as people will pick up products and test them (for purchase) simply by pressing the keys, discounting the product if the keys don't “feel” right.
It is further desirable to configure each “traditional” key to provide multiple outputs, preferably up to five outputs per key. By “traditional key” I mean a discrete key or key region disposed over an associated switch element such that when the key is pressed, the switch is closed. Typically, such keys also have associated, discrete tactile feedback elements, some of which (such as poly or metal snap domes) also provide the discrete switch function.
Some keypad layouts and key associations have developed universal recognition as a standard. For example, the standard 12-key telephone keypad layout has established an association between numbers and letters, the letters “ABC” being associated with the number “2”, “PQRS” associated with the number “7”, and so forth. Throughout this application, the telephone keypad is used as an example of one application of the present invention. However, the technology is not necessarily limited to use with telephone keypads, but is applicable to any keypad with keys having associated central functions (e.g., the “numbers” of the telephone keypad) and peripheral functions (e.g., the letters of the telephone keypad). Any symbols, alphanumeric or others, may be used.